As I know it, Mercedes cars are expensive to fix when they break, but this is offset by the great engineering and reliability, so that over time, the running costs are generally not that much greater than e.g. a Ford.....true?
To keep a Mercedes-Benz running in top shape is going to cost you, and by this I mean A LOT!
It gets worse on older models, as all rubber elements (i.e. suspension components as said before, window seals, door seals, engine mounts, hoses, etc, etc, etc.) fail rapidly, and if not taking care of, the car will just quit on you.
Be very, very careful. Select a car with a full history and low mileage if possible. If not, be prepared to spend at least the same amount of money you paid for the car to have it fixed.
I have owned Mercedes T wagons for almost 20 years now (W123 and W124s) and they are NOT low maintenance toys. They actually tend to be more demanding than the equivalent sedans in their range.
CL 500, 1998
S 500 L, 1998
E 320 T, 1995